1. Field of the Invention
The present invention relates to a thin film capacitor, a thin film capacitor-embedded printed circuit board and a manufacturing method of the thin film capacitor, and more particularly, to a thin film capacitor capable of attaining a desired dielectric constant without high temperature heat treatment and improved in leakage current characteristics, a thin film capacitor-embedded printed circuit board and a manufacturing method of the thin film capacitor.
2. Description of the Related Art
Various kinds of passive devices mounted on a printed circuit board significantly obstruct miniaturization of products. Particularly, with semiconductor active devices increasingly embedded and the number of input and output terminals rising, the passive devices are required to occupy more space around the active devices. A representative example of passive devices includes a capacitor. The capacitor may be advantageously disposed within the closest proximity to the input terminal to reduce induced inductance resulting from a higher operating frequency.
To satisfy such a demand for small size and higher frequency, recently, studies have been vigorously conducted on a method of manufacturing an embedded capacitor. The embedded capacitor is embedded in the printed circuit board and dramatically reduces size of the product. Also, the embedded capacitor can be placed in a vicinity to the input terminal of the active device, and thus a length of conductive line may be minimized to thereby considerably lower induced inductance and eliminate high frequency noise.
As a conventional method for manufacturing this embedded capacitor, ferroelectrics with high permittivity have been dispersed in the resin. However even in this case, such a capacitor can be hardly embedded in the printed circuit board due to limited capacitance.
That is, ferroelectrics such as BaTiO3 are noticeably superior in dielectric constant characteristics to paraelectrics. But to attain these excellent dielectric constant characteristics, the ferroelectrics should be treated at a temperature of e.g., 550° C. However, such heat treatment is hardly applicable to a printed circuit board employing a current substrate using polymer such as resin due to lack of heat resistance of the resin.
Paraelectrics such as SiO2, Al2O3 and Ta2O5 are considerably low in dielectric constant. For example, SiO2 has a dielectric constant of 3.9. Here, the paraelectrics may be heat treated to increase a dielectric constant thereof but is hardly capable of attaining a dielectric constant for a general capacitor.
Therefore, to form a capacitor-embedded printed circuit board, there has been a consistent request for developing a thin film capacitor including a dielectric layer with superior leakage current characteristics while having a desired dielectric constant without being heat-treated at a high temperature.